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Chapter 4
BRINGING AC ELECTRICAL ON BOARD-EARLIER & LATER SYSTEMS
TYPICAL EARLIER SYSTEM
To this point we have covered the process of bringing
AC electricity from the marina dock power center to the
yacht shore power inlet or to the optional cord reel.
From the above point of entry earlier 46 SC yachts use
a system to distribute AC electricity that may included
a double pole single throw inlet breaker, isolation trans-
former, triple pole single throw breaker after the trans-
former and a ship’s AC main control panel with shore
power main and auxiliary equipment
breakers.
After the inlet or the cord reel AC elec-
tricity travels to a 2 pole single throw
breaker located above the swim plat-
form in the starboard stairway locker.
At this point it travels to the primary
side of the isolation transformer.
The isolation transformer is located in
the engine room (bilge). See
the illustration. The isola-
tion transformer is used to
isolate the AC shore power
from the yacht’s AC pow-
er. AC electrical power is
transferred by the use of
magnetic coupling. Basical-
ly, there is no direct electri-
cal connection between the
shore side, earth grounded
AC power and the yacht’s
AC power system.
The shore grounding is connected to a shield between
the primary (shore) and secondary (yacht) transformer
windings. This shield isolates and therefore reduces gal-
vanic corrosion.
ISOLATION
TRANSFORMER
By grounding one leg of the
transformer on the secondary
side the “creation” of a neu-
tral exists. The “neutral” wire
(blue) along with the 2 conduc-
tor (red & brown) wires travel
to a triple pole breaker located
at the output side of the transformer and eventually to
the main AC control panel. The green earth (bonding)
ground is connected as another continuing leg of the AC
grounding side of the circuit.
See the drawing on the next page for more AC circuit
information.
TRIPLE POLE BKR.
DOUBLE
POLE BKR.
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